Method and apparatus for transmitting and receiving status report in a mobile communication system

ABSTRACT

A method and apparatus for transmitting/receiving a status report in a mobile communication system where Automatic Repeat reQuest (ARQ) and Hybrid Automatic Repeat reQuest (HARQ) operate together. An ARQ receiving (Rx) entity determines whether transmission of the status report is permitted, if a predetermined status report generation condition is satisfied. If the transmission of the status report is permitted, the ARQ Rx entity generates a status report depending on a reception status of ARQ packets received up to the time the transmission of the status report is permitted, and transmits the generated status report to an ARQ transmitting (Tx) entity through an allocated transmission resource. The ARQ Tx entity determines an initial reception time of an HARQ packet including the status report as a generation time of the status report, and performs retransmission according to the status report.

PRIORITY

This application claims priority under 35 U.S.C. §119(a) to a KoreanPatent Application filed in the Korean Intellectual Property Office onApr. 14, 2006, entitled “Method and Apparatus for Transmitting andReceiving Status Report in a Mobile Communication System” and assignedSerial No. 2006-33964, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a mobile communicationsystem, and in particular, to a method and apparatus for transmittingand receiving a status report of Automatic Repeat reQuest (ARQ) in anARQ layer.

2. Description of the Related Art

The Universal Mobile Telecommunication Service (UMTS) system, which is a3^(rd) Generation (3G) asynchronous mobile communication system, usesWideband Code Division Multiple Access (WCDMA). UMTS is based on GlobalSystem for Mobile Communications (GSM) and General Packet Radio Services(GPRS), both of which are European mobile communication systems.

Within the 3^(rd) Generation Partnership Project (3GPP) in charge ofUMTS standardization, Long Term Evolution (LTE) is being discussed asthe next generation mobile communication system of the UMTS system. LTE,aimed for deployment in around 2010, is a technology for implementinghigh-speed packet based communication at about 100 Mbps. To this end,several schemes are under discussion, including one scheme for reducingthe number of nodes located in a communication path by simplifying thenetwork configuration, and another scheme for maximally implementingwireless protocols to wireless channels.

FIG. 1 is an overview of a configuration of an Evolved UMTS (E-UMTS)mobile communication system.

Referring to FIG. 1, a configuration of Evolved UMTS Radio AccessNetworks (E-UTRANs or E-RAN) 135 and 140 is simplified to a 2-nodeconfiguration of Evolved Node Bs (ENBs or Node Bs) 110 to 130, andanchor nodes 145 and 150. A User Equipment (UE) 105 accesses an InternetProtocol (IP) network by E-RAN 135 and 140.

ENBs 110 to 130, nodes corresponding to the existing Node Bs, areconnected to UE 105 over a wireless channel. Compared with the existingNode Bs, ENBs 110 to 130 perform more complex functions.

In LTE, all user traffics, including real-time services such as Voiceover IP (VoIP) service, are serviced over a shared channel. This meansthat there is a need for an apparatus for collecting status informationof UEs and performing scheduling depending thereon, and the schedulingis managed by ENBs 110 to 130. The terms ‘ENB’ and ‘Node B’ are hereinused interchangeably.

In LTE, like in High Speed Downlink Packet Access (HSDPA) or EnhancedUplink Dedicated Channel (EDCH), Hybrid Automatic Repeat reQuest (HARQ)is performed between ENBs 110 to 130 and UE 105. However, with use ofonly the HARQ, LTE cannot satisfy the various Quality of Service (QoS)requirements. Therefore, a separate ARQ (or outer-ARQ) can be performedin an upper layer, and outer-ARQ is also performed between ENBs 110 to130 and UE 105.

It is expected that LTE will use Orthogonal Frequency DivisionMultiplexing (OFDM) as wireless access technology in a 20-MHz bandwidthin order to realize a data rate of a maximum of 100 Mbps. In addition,LTE will employ Adaptive Modulation & Coding (AMC) that determines amodulation scheme and a channel coding rate according to channel statusof UEs. Many mobile communication systems now under discussion,including LTE, use both HARQ and ARQ as an error correction technique.

HARQ is a technique for soft-combining previously received data withretransmitted data without discarding the previously received data,thereby increasing the reception success rate. More specifically, anHARQ receiving (Rx) entity determines presence/absence of error in areceived packet, and sends an Acknowledged (ACK) signal or aNon-Acknowledged (NACK) signal to an HARQ transmitting (Tx) entityaccording to the presence/absence of error. The HARQ Tx entity performsretransmission of the HARQ packet or transmission of a new HARQ packetaccording to the HARQ ACK/NACK signal. HARQ is characterized in that itsoft-combines a retransmitted packet with a previously received packet,thereby reducing the error rate.

However, ARQ, a technique for checking the sequence number of a receivedpacket and sending the retransmission request for a missing packet usinga status report, does not soft-combine a previously received packet witha retransmitted packet. 4

Because both ARQ and HARQ have a function of recovering erroneouspackets, it is considered that there is no need to perform ARQ and HARQtogether. However, because a sufficiently low packet error ratio cannotbe obtained with only using HARQ, ARQ and HARQ should be performedtogether in most packet services.

In HARQ, because an HARQ ACK/NACK signal is a 1-bit response signal, itis difficult to reduce the error rate through channel coding. Therefore,it is hard to achieve a low packet error rate with use of only HARQ.That is, if an HARQ NACK signal is misrecognized as an HARQ ACK signal,the corresponding packet is completely lost at the HARQ layer.Therefore, reliability of the HARQ ACK/NACK signal acts as an importantfactor in determining a packet error ratio in the HARQ layer.

The system, in which ARQ and HARQ operate together, can increaseefficiency of an ARQ operation using information from the HARQ layer.For example, an HARQ Tx entity sends transmission complete timeinformation for an ARQ packet to an ARQ transmitting (Tx) entity, andthe ARQ Tx entity compares the time the status report has occurred, withthe time the ARQ packet transmission is completed, thereby preventingunnecessary retransmission.

If occurrence and transmission of the status report are achieved duringthe same time, the time the HARQ packet containing the status report wasinitially received is substantially equal to the time the status reporthas occurred. However, if the occurrence time of the status report isdifferent from the transmission time of the status report, the ARQ Txentity cannot estimate the occurrence time of the status report, andmerely recognizes, as the occurrence time of the status report, the timethe HARQ packet containing the status report was initially received.

For example, reception of success/failure information for specific ARQpacket(s), received for a delayed time from the occurrence time to thetransmission time of the status report at the ARQ receiving (Rx) entity,cannot be included in the previously generated status report. Becausethe status report has no reception of success/failure information forthe specific ARQ packet; the ARQ Tx entity retransmits the specific ARQpacket to the ARQ Rx entity, considering that it has failed to transmitthe specific ARQ packet. Therefore, the conventional mobilecommunication system may experience unnecessary retransmission.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the aboveproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present invention is toprovide a method and apparatus in which an ARQ receiving (Rx) entitygenerates and sends a status report at the time when it cansubstantially send the status report in a mobile communication system.

Another aspect of the present invention is to provide a method andapparatus in which an ARQ transmitting (Tx) entity estimates theoccurrence time of a status report after receiving the status report ina mobile communication system.

Another aspect of the present invention is to provide a method andapparatus in which the ARQ Tx entity estimates the time a status reporthas occurred in an HARQ layer, in a mobile communication system whereARQ and HARQ operate together.

Another aspect of the present invention is to provide a method andapparatus in which an ARQ Tx entity removes the time error due to ascheduling delay of an HARQ packet when it estimates the occurrence timeof a status report at an initial reception time of the HARQ packetcontaining the status report in a mobile communication system where ARQand HARQ operate together.

According to one aspect of the present invention, there is provided amethod for transmitting the status report of an Automatic Repeat reQuest(ARQ) layer in a mobile communication system including the ARQ layer anda Hybrid Automatic Repeat reQuest (HARQ) layer. The transmission methodincludes determining by an ARQ receiving (Rx) entity whethertransmission of the status report is permitted, when a predeterminedstatus report generation condition is satisfied; if transmission of thestatus report is permitted, generating a status report depending on areception status of ARQ packets up to the time the transmission of thestatus report is permitted; and transmitting the generated status reportto an ARQ transmitting (Tx) entity through an allocated transmissionresource.

According to another aspect of the present invention, there is provideda method for receiving the status report of an Automatic Repeat reQuest(ARQ) layer in a mobile communication system including the ARQ layer anda Hybrid Automatic Repeat reQuest (HARQ) layer. The reception methodincludes recording, by a transmitting HARQ transmitting/receiving(Tx/Rx) entity, the initial reception time of an HARQ packet, when theHARQ packet is initially received from an ARQ receiving (Rx) entity; ifit is determined that the HARQ packet has been successfully received,detecting the status report contained in the HARQ packet, and sendingthe detected status report to an ARQ transmitting (Tx) entity togetherwith the initial reception time of the HARQ packet; and recognizing, bythe ARQ Tx entity, the initial reception time as a generation time ofthe status report, and retransmitting retransmission-requested ARQpackets according to the status report.

According to a further aspect of the present invention, there isprovided an apparatus for transmitting a status report of an AutomaticRepeat reQuest (ARQ) layer in a mobile communication system includingthe ARQ layer and a Hybrid Automatic Repeat reQuest (HARQ) layer. Thetransmission apparatus includes a status report generator fordetermining whether transmission of the status report is permitted, whena predetermined status report generation condition is satisfied in anARQ receiving (Rx) entity, and if transmission of the status report ispermitted, generating a status report depending on the reception statusof ARQ packets up to the time the transmission of the status report ispermitted; and a transmitting entity for transmitting the generatedstatus report to an ARQ transmitting (Tx) entity through an allocatedtransmission resource.

According to yet another aspect of the present invention, there isprovided an apparatus for receiving a status report of an AutomaticRepeat reQuest (ARQ) layer in a mobile communication system includingthe ARQ layer and a Hybrid Automatic Repeat reQuest (HARQ) layer. Thereception apparatus includes an HARQ transmitting/receiving (Tx/Rx)entity for recording the initial reception time of the HARQ packet, whenan HARQ packet is initially received from an ARQ receiving (Rx) entity,and if it is determined that the HARQ packet has been successfullyreceived, detecting the status report contained in the HARQ packet, andoutputting the detected status report together with the initialreception time of the HARQ packet; and an ARQ transmitting (Tx) entityfor recognizing the initial reception time as a generation time of thestatus report, and retransmitting retransmission-requested ARQ packetsaccording to the status report.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is an overview of a configuration of an Evolved UMTS mobilecommunication system;

FIG. 2 is a flow diagram illustrating a status report transmissionprocedure in a general mobile communication system;

FIG. 3 is a flow diagram illustrating a status report transmissionprocedure according to the present invention;

FIG. 4 is a flowchart of a generation and transmission process of astatus report in an ARQ Rx entity according to the present invention;

FIG. 5 is a flowchart of an operation of an HARQ Rx entity according tothe present invention;

FIG. 6 is a flowchart of an operation of an ARQ Tx entity according tothe present invention; and

FIG. 7 is a block diagram illustrating a structure of an ARQ Tx/Rxentity according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail with reference to the annexed drawings. In the followingdescription, detailed description of known functions and configurationshas been omitted for clarity and conciseness.

The present invention provides a scheme in which an ARQ transmittingentity removes an error due to the scheduling delay of a status reportwhen it estimates the time the status report has occurred in an HARQlayer in a mobile communication system where ARQ and HARQ operatetogether.

Referring to FIG. 2, the illustrated status report transmissionprocedure includes a scheduling delay. An ARQ transmitting (Tx) entity205 transmits in step 225 an ARQ packet(s) to an ARQ receiving (Rx)entity 220 via HARQ transmitting/receiving (Tx/Rx) entities 210 and 215.In 3GPP, the term ‘Protocol Data Unit (PDU)’ is generally used insteadof the term ‘packet’. Thus, in the present invention, the terms ‘packet’and ‘PDU’ will be used together. In step 230, if any one ofpredetermined status report generation conditions is satisfied, ARQ Rxentity 220 triggers the generation of a status report, and then sendsthe status report to ARQ Tx entity 205, to request retransmission ofmissing (or reception-failed) ARQ PDUs and/or to notify of successfullyreceived ARQ PDUs.

The conditions on which ARQ Rx entity 220 generates a status report canbe defined in a call setup process, and the conditions can include thefollowing conditions.

-   -   ARQ Rx entity 220 generates a status report upon detecting a        missing ARQ PDU.    -   ARQ Rx entity 220 generates a status report at stated periods.

If any one of the status report generation conditions is satisfied, ARQRx entity 220 triggers generation of a status report.

Preferably, the status report is sent upon its generation. However, in acommunication system to which ENB scheduling is applied, like in LTE,there is a high possibility that a scheduling delay 235 will be applied.For example, if a UE including ARQ Rx entity 220 has no allocatedtransmission resource at time 230 the status report is generated, the UEshould first go through a scheduling process of issuing a request fortransmission resource and receiving allocated transmission resource, andscheduling delay 235 of a minimum of several tens of msec may berequired in the scheduling process.

After ARQ Rx entity 220 experiences scheduling delay 235, the statusreport is contained in an HARQ packet in step 240, and then finally sentto HARQ Tx/Rx entity 210, a lower layer of the ARQ Tx entity 205, byHARQ Tx/Rx entity 215.

In the following description, it is assumed that an HARQ packetcontaining the status report succeeds in reception to ARQ Tx entity 205through 3 repeated transmissions, by way of example.

That is, if ARQ Rx entity 220 sends the status report to receiving HARQTx/Rx entity 215 (i.e. HARQ Tx/Rx entity in the receiving entity) instep 240, receiving HARQ Tx/Rx entity 215 contains the status report inan HARQ packet and sends the HARQ packet to transmitting HARQ Tx/Rxentity 210 (i.e. HARQ Tx/Rx entity in the transmitting entity) in step245 (1^(st) Transmission). Transmitting HARQ Tx/Rx entity 210 checks instep 250 an initial reception time at which it has initially receivedthe HARQ packet, and determines whether the HARQ packet has beensuccessfully received without error. If it is determined thattransmitting HARQ Tx/Rx entity 210 has failed in the successfulreception of the HARQ packet, transmitting HARQ Tx/Rx entity 210 sendsin step 255 a NACK to receiving HARQ Tx/Rx entity 215, and in responseto the NACK, receiving HARQ Tx/Rx entity 215 retransmits in step 260 theHARQ packet to transmitting HARQ Tx/Rx entity 210 (2^(nd) Transmission).Transmitting HARQ Tx/Rx entity 210 combines the second-transmitted HARQpacket with the first-transmitted HARQ packet, and then determineswhether the HARQ packet has been successfully received.

If transmitting HARQ Tx/Rx entity 210 has failed again in the successfulreception of the HARQ packet, transmitting HARQ Tx/Rx entity 210 sendsagain a NACK to the receiving HARQ Tx/Rx entity 215 in step 265. Inresponse to the NACK, the receiving HARQ Tx/Rx entity 215 retransmitsagain the HARQ packet to transmitting HARQ Tx/Rx entity 210 in step 270(3^(rd) Transmission). If transmitting HARQ Tx/Rx entity 210 has nowsucceeded in reception of the HARQ packet, transmitting HARQ Tx/Rxentity 210 extracts a status report contained in the HARQ packet andsends the extracted status report to the ARQ Tx entity 205 in step 275,and then sends an ACK for the HARQ packet to the receiving HARQ Tx/Rxentity 215 in step 280.

ARQ Tx entity 205 prevents unnecessary retransmission of an ARQ PDU byrecognizing the status report generation time 230 at-which the statusreport is generated. As for status report generation time 230, it isexplicitly expressed in the status report, or HARQ Tx entity 205estimates status report generation time 230 using initial reception time250 of the HARQ packet containing the status report. However, the methodof using initial reception time 250 of the HARQ packet is inaccurate asscheduling delay 235 applied to the status report is disregarded.

Therefore, the preferred embodiment of the present invention removes theerror due to the scheduling delay applied to a status report, whenestimating the status report generation time from the initial receptiontime of an HARQ packet containing the status report. That is, eventhough the status report generation condition is satisfied, the ARQ Rxentity does not immediately generate the status report, but generates astatus report after preparing for its transmission, like allocation oftransmission resource, is completed. In addition, the ARQ Tx entityrecognizes, as a status report generation time, an initial receptiontime of an HARQ packet containing a status report.

Referring to FIG. 3, the status report is triggered in step 325, if oneof status report generation conditions is satisfied in ARQ Rx entity320. The status report generation condition can be periodical generationof a status report, or discovery of a missing ARQ PDU. Even though theistatus report is triggered, ARQ Rx entity 320 performs the followingoperation without immediately generating a status report.

That is, ARQ Rx entity 320 reports presence of transmission data to alower layer (not shown), and the lower layer permits ARQ Rx entity 320to deliver the transmission data if there is any transmission resourceactually allocated. For example, the lower layer, an entity in charge ofmanagement of transmission resources, is a scheduler in an ENB, and is atransmission resource manager in the UE. If there is no transmissionresource allocated at the present time at which ARQ Rx entity 320reports presence of transmission data, the lower layer is allocated atransmission resource through an appropriate process. If ARQ Rx entity320 belongs to a UE, the lower layer sends an allocation request fortransmission resource to an ENB, and waits until transmission resourceis allocated from the ENB. If transmission resource is allocated, thelower layer permits ARQ Rx entity 320 to deliver the transmission data.

Upon acquiring transmission approval from the lower layer, ARQ Rx entity320 generates a status report in step 330. The status report containssequence numbers of missing ARQ PDUs for retransmission request, andsequence numbers of ARQ PDUs successfully received up to the time thestatus report is generated. The missing ARQ PDU refers to areception-failed (or NACK-ed) ARQ PDU, and the ARQ PDU, reception ofwhich is unknown, does not correspond to the missing ARQ PDU.

ARQ Rx entity 320 sends the status report to a receiving HARQ Tx/Rxentity 315 in step 335, and receiving HARQ Tx/Rx entity 315 generates anHARQ packet containing the status report and then transmits the HARQpacket to a transmitting HARQ Tx/Rx entity 310 using an allocatedtransmission resource in step 345.

Transmitting HARQ Tx/Rx entity 310 records an initial reception time 340of the HARQ packet, and determines if the HARQ packet has beensuccessfully received. If the HARQ packet has been successfullyreceived, transmitting HARQ Tx/Rx entity 310 sends in step 350 initialreception time 340 of the HARQ packet to an ARQ Tx entity 305 togetherwith the status report contained in the HARQ packet.

In step 355, ARQ Tx entity 305 recognizes, as the status reportgeneration time, initial reception time 340 transmitted in step 350together with the status report. If there is an ARQ PDU, which wastransmitted before the status report generation time but has not beenACK-ed yet by the status report, ARQ Tx entity 305 determines that theARQ PDU needs retransmission.

Referring to FIG. 4, a status report generation condition is satisfiedand a generation of the status report is triggered in step 405, and thenan ARQ Rx entity reports in step 410 the presence of transmission datato a lower layer in charge of management of transmission resources. Thetransmission data includes a status report to be transmitted. If thelower layer permits data transmission in step 415 by allocatingtransmission resource to be used for transmission of data including astatus report, ARQ Rx entity proceeds to step 420, and if datatransmission is not permitted, the ARQ Rx entity waits until the datatransmission is permitted. For example, if a UE including the ARQ Rxentity is scheduled in the current transmission time interval, or if anENB including the ARQ Rx entity has scheduled a UE that will transmitthe status report, the ARQ Rx entity determines that transmission ofdata including the status report is possible.

In step 420, the ARQ Rx entity generates a status report depending onthe ARQ PDU reception status up to the present time. The status reportcontains sequence numbers of ARQ PDUs successfully received up to thepresent time, i.e. ACK-ed ARQ PDUs, and sequence numbers of ARQ PDUsreception-failed up to the present time, i.e. NACK-ed ARQ PDUs, forwhich the status report is generated. Because the ARQ Rx entity cannotrecognize the existence of the ARQ PDU that is in an HARQ procedure inits lower HARQ Tx/Rx entity or is completely lost in a delivery process,the ARQ Rx entity does not include a sequence number of the ARQ PDU inthe status report. Thereafter, in step 425, the ARQ Rx entity forwardsthe status report to its lower HARQ Tx/Rx entity, and the HARQ Tx/Rxentity contains the status report in an HARQ packet and sends the HARQpacket to an ARQ Tx entity via a counterpart HARQ Tx/Rx entity.

To sum up, if the status report generation condition is satisfied, theARQ Rx entity waits until the time it can actually send the statusreport, and generates a status report at the time it can send the statusreport. In this manner, the ARQ Rx entity maximally approaches the timethe status report is generated, to the time the transmission of thestatus report is started. Therefore, the ARQ Tx entity can determinethat the ‘status report reception time’ is substantially equal to the‘status report generation time’. The propagation delay may be taken intoconsideration between the time the HARQ packet including the statusreport is sent from the receiving HARQ Tx/Rx entity, and the time theHARQ packet is received at the transmitting HARQ Tx/Rx entity. However,this is not related to the present invention, so a detailed descriptionthereof will be omitted.

Referring to FIG. 5, a new HARQ packet is received in step 505, i.e. ifthe HARQ packet is initially received, and then a HARQ Tx/Rx entityrecords an initial reception time of the HARQ packet in step 510.

The HARQ Tx/Rx entity recognizes the reception of the new HARQ packetdepending on the decoding control information of the HARQ packet,transmitted over a control channel, like Retransmission Sequence Number(RSN) or New Data Indicator (NDI). For example, if RSN is set to ‘0’ orNDI is set to a different value from the previous value, it means thattransmission of a new HARQ packet starts.

In step 515, the HARQ Tx/Rx entity performs an HARQ reception process onthe HARQ packet. That is, the HARQ Tx/Rx entity determinespresence/absence of error in the HARQ packet through Cyclic RedundancyChecking (CRC) on the HARQ packet. If there is a CRC error, the HARQTx/Rx entity stores the HARQ packet in a soft buffer of thecorresponding HARQ processor, for soft combining. However, if there isno CRC error, the HARQ Tx/Rx entity processes and forwards the HARQpacket to its upper layer.

If reception of the HARQ packet is successful in step 520, i.e. there isno more error in the HARQ packet, the HARQ Tx/Rx entity proceeds to step525 where it demultiplexes the upper layer data contained in the HARQpacket. Thereafter, in step 530, the HARQ Tx/Rx entity forwards thedemultiplexed upper layer data to an appropriate upper layer. Inparticular, the status report in the demultiplexed upper layer data issent to an ARQ Tx entity. At this point, the initial reception time ofthe HARQ packet, recorded in step 510, is sent to the ARQ Tx entitytogether. In step 535, the HARQ Tx/Rx entity clears the initialreception time recorded in step 510, and then proceeds to step 540 whereit flushes the soft buffer of the HARQ processor.

If the reception of the HARQ packet has failed in step 520, i.e. iftransmission of a new HARQ packet is started even though there is stillan error in the HARQ packet, the HARQ Tx/Rx entity clears the initialreception time for the HARQ packet in step 535, and flushes the softbuffer of the HARQ processor in step 540.

Referring to FIG. 6, if an ARQ Tx entity receives in step 605 a statusreport and an initial reception time from a transmitting HARQ Tx/Rxentity, which is its lower layer, the ARQ Tx entity recognizes in step610 the initial reception time as a status report generation time, andperforms the necessary operation according to the content of the statusreport. In other words, the ARQ Tx entity retransmits the missing ARQPDUs indicated in the status report, and the ARQ PDU that wastransmitted before the status report generation time but has not beenACK-ed by the status report.

The term ‘time’ used throughout the specification will now be describedin more detail.

The present invention uses multiple segments of ‘time’ that should beequally recognized by a UE and an ENB, like ‘status report generationtime’, ‘initial reception time’ and ‘transmission complete time’. As thesimplest way of allowing an index indicating a certain time to have thesame meaning between two nodes, the UE and the ENB include timerssynchronized with each other. However, in general mobile communication,it is more accepted that the UE uses the system time broadcasted by theENB, rather than using the individual synchronized timers.

In mobile communication, a frame is used as a time unit. The frame meansa period used as a basic unit for transmission/reception. For example,in UMTS, one-frame length is 10 msec.

In the conventional mobile communication system, like in UMTS, the ENBincludes a timer (or counter) that increases by 1 at every frameboundary. The timer increases by 1 every 10 msec, and the timer startsat the initiation of the frame. An output value of the timer isincreased by 1 at every frame boundary, and is called a frame number. Asthe ENB periodically broadcasts the frame number, the UE and the ENB canidentify the frame number for a specific frame.

Therefore, the frame number broadcasted by the ENB can be used as the‘time’ described in the present invention. For example, the statusreport generation time can be replaced with a frame number of the frameat which the status report is generated, and the transmission completiontime can be replaced with a frame number of the transmission-completedframe. Specifically, the frame number be hierarchically structured. Forexample, in LTE, because the transmission/reception unit has a shortperiod of 0.5 msec, the system uses a period longer than 10 msec as aunit of a frame rather than recognizing a frame in units of 0.5 msec,and can use 0.5 msec as a unit of a sub-frame. That is, in a systemwhere one frame having a 10-msec length is composed of 20 sub-frameshaving a 0.5-msec length, the combination of a frame number and asub-frame number can be used as an index of time. For example, the time2505.11 means a sub-frame #11 in a frame #2505.

As illustrated in FIG. 7, an ARQ entity 700 includes a transmissioncontroller 705, a transmission buffer 710, a framing unit 715, aretransmission buffer 720, a status report generator 740, and areception buffer 745. ARQ entity 700 is connected to a multiplexer 725and a demultiplexer 750. Although only one ARQ entity 700 is shownherein, multiple undepicted ARQ entities can be provided. Multiplexer725 multiplexes ARQ packets (i.e. ARQ PDUs) delivered from multiple ARQentities 700 into one HARQ packet, and demultiplexer 750 demultiplexesan HARQ packet delivered from an HARQ processor 730 into multiple ARQpackets (i.e. ARQ PDUs), and delivers the ARQ packets to theirassociated ARQ entities.

HARQ processor 730 is a device for transmitting/receiving an HARQ packetthrough a specific HARQ operation, and a transceiver 735 is a device formodulating an HARQ packet into a radio signal before transmission, anddemodulating a received radio signal. Demultiplexer 750 stores thereceived ARQ PDU in reception buffer 745.

Status report generator 740, if any one of predetermined status reportgeneration conditions is satisfied, reports to transmission controller705 that a status report is triggered. Thereafter, if transmissioncontroller 705 permits transmission of a status report, status reportgenerator 740 checks sequence numbers of the ARQ PDUs stored inreception buffer 745, recognizes sequence numbers of successfullyreceived ARQ PDUs and sequence numbers of ARQ PDUs to be requested forretransmission, and generates a status report according thereto. Statusreport generator 740 sends the generated status report to counterpartnode via the multiplexer 725.

A packet generated in the upper layer is stored in transmission buffer710. The upper layer packet is framed in an appropriate size by framingunit 715, configured into an ARQ packet having header informationincluding a sequence number inserted therein, and then delivered tomultiplexer 725. A copy of the ARQ packet is stored in retransmissionbuffer 720.

Transmission controller 705 analyzes a trigger report on the statusreport delivered from status report generator 740, and controls datatransmission of transmission buffer 710 and retransmission buffer 720depending on the analysis result. Specifically, transmission controller705 reports, to the lower layer, the amount of data stored in buffers710 and 720, and based on the amount of data transmittable in the nexttransmission period, reported from the lower layer, transmissioncontroller 705 determines data to be transmitted in the nexttransmission period, and controls buffers 710 and 720 to outputappropriate data. The amount of transmittable data is determinedaccording to the allocated transmission resource.

In particular, upon receipt of a trigger report for the status reportfrom status report generator 740, transmission controller 705, ifpermission for data transmission is received from a lower layer, reportsit to status report generator 740 so as to generate a status report.Therefore, in ARQ entity 700, at the time the data transmission isactually permitted, status report generator 740 generates a statusreport, and the status report is immediately sent using the allocatedtransmission resource.

In the mobile communication system to which ENB scheduling is applied,the present invention matches the time the status report is generated inthe ARQ Rx entity, to the time the status report is actuallytransmitted, so that the ARQ Tx entity can find the time the statusreport is generated, from the initial reception time of an HARQ packetcontaining the status report, and can minimize inefficiency due to theincorrect status report.

As can be understood from the foregoing description, the ARQ Rx entitygenerates and sends a status report after a scheduling delay, and theARQ Tx entity estimates, as a generation time of the status report, theinitial reception time of an HARQ packet containing the status report,thereby preventing unnecessary retransmission due to an error betweenthe status report generation time and the initial reception time.

While the invention has been shown and described with reference to acertain preferred embodiment thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asfurther defined by the appended claims.

1. A method for transmitting a status report of an Automatic RepeatreQuest (ARQ) layer in a mobile communication system including the ARQlayer and a Hybrid Automatic Repeat reQuest (HARQ) layer, the methodcomprising: determining whether transmission of the status report ispermitted, when a predetermined status report generation condition issatisfied in an ARQ receiving (Rx) entity; if transmission of the statusreport is permitted, generating a status report depending on a receptionstatus of ARQ packets up to the time the transmission of the statusreport is permitted; and transmitting the generated status report to anARQ transmitting (Tx) entity through an allocated transmission resource.2. The method of claim 1, wherein the status report includes sequencenumbers of ARQ packets successfully received up to the time thetransmission of the status report is permitted, and sequence numbers ofARQ packets reception-failed up to the time the transmission of thestatus report is permitted.
 3. The method of claim 1, wherein the timethe transmission of the status report is permitted, indicates the timeat which a transmission resource used for transmitting data includingthe status report is allocated.
 4. The method of claim 1, furthercomprising: determining that the status report generation condition issatisfied, when a present time reaches a transmission time intervalbased on a predetermined period.
 5. The method of claim 1, furthercomprising: determining that the status report generation condition issatisfied, when a missing ARQ packet is detected in the course ofreceiving ARQ packets from the ARQ Tx entity.
 6. A method for receivinga status report of an Automatic Repeat reQuest (ARQ) layer in a mobilecommunication system including the ARQ layer and a Hybrid AutomaticRepeat reQuest (HARQ) layer, the method comprising: recording, by anHARQ transmitting/receiving (Tx/Rx) entity, an initial reception time ofan HARQ packet, when the HARQ packet is initially received from an ARQreceiving (Rx) entity; detecting a status report contained in the HARQpacket if it is determined that the HARQ packet has been successfullyreceived, and sending the detected status report to an ARQ transmitting(Tx) entity together with the initial reception time of the HARQ packet;and recognizing, by the ARQ Tx entity, the initial reception time as ageneration time of the status report, and retransmittingretransmission-requested ARQ packets according to the status report. 7.The method of claim 6, wherein the status report includes sequencenumbers of ARQ packets successfully received at the ARQ Rx entity up tothe time the transmission of the status report is permitted, andsequence numbers of failed ARQ packets at the ARQ Rx entity up to thetime the transmission of the status report is permitted.
 8. The methodof claim 7, wherein the time the transmission of the status report ispermitted, indicates a time at which a transmission resource used fortransmitting data including the status report is allocated.
 9. Themethod of claim 6, further comprising: receiving decoding controlinformation of the HARQ packet over a control channel, and checking aRetransmission Sequence Number (RSN) and a New Data Indicator (NDI)included in the decoding control information; and determining that theHARQ packet has been initially received, if the RSN is set to ‘0’ or theNDI is set to a different value from a previous value.
 10. An apparatusfor transmitting a status report of an Automatic Repeat reQuest (ARQ)layer in a mobile communication system including the ARQ layer and aHybrid Automatic Repeat reQuest (HARQ) layer, the apparatus comprising:a status report generator for determining whether transmission of thestatus report is permitted, when a predetermined status reportgeneration condition is satisfied in an ARQ receiving (Rx) entity, andif transmission of the status report is permitted, generating a statusreport depending on a reception status of ARQ packets up to the time thetransmission of the status report is permitted; and a transmittingentity for transmitting the generated status report to an ARQtransmitting (Tx) entity through an allocated transmission resource. 11.The apparatus of claim 10, wherein the status report includes sequencenumbers of ARQ packets successfully received up to the time thetransmission of the status report is permitted, and sequence numbers ofARQ packets reception-failed up to the time the transmission of thestatus report is permitted.
 12. The apparatus of claim 10, wherein thetime the transmission of the status report is permitted, indicates atime at which a transmission resource used for transmitting dataincluding the status report is allocated.
 13. The apparatus of claim 10,wherein the status report generator determines that the status reportgeneration condition is satisfied, when a present time reaches atransmission time interval based on a predetermined period.
 14. Theapparatus of claim 10, wherein the status report generator determinesthat the status report generation condition is satisfied, when a missingARQ packet is detected in the course of receiving ARQ packets from theARQ Tx entity.
 15. An apparatus for receiving a status report of anAutomatic Repeat reQuest (ARQ) layer in a mobile communication systemincluding the ARQ layer and a Hybrid Automatic Repeat reQuest (HARQ)layer, the apparatus comprising: an HARQ transmitting/receiving (Tx/Rx)entity for recording an initial reception time of the HARQ packet, whenan HARQ packet is initially received from an ARQ receiving (Rx) entity,and if it is determined that the HARQ packet has been successfullyreceived, detecting a status report contained in the HARQ packet, andoutputting the detected status report together with the initialreception time of the HARQ packet; and an ARQ transmitting (Tx) entityfor recognizing the initial reception time as a generation time of thestatus report, and retransmitting retransmission-requested ARQ packetsaccording to the status report.
 16. The apparatus of claim 15, whereinthe status report includes sequence numbers of ARQ packets successfullyreceived at the ARQ Rx entity up to the time the transmission of thestatus report is permitted, and sequence numbers of ARQ packets failedto be received at the ARQ Rx entity up to the time the transmission ofthe status report is permitted.
 17. The apparatus of claim 16, whereinthe time the transmission of the status report is permitted, indicates atime at which a transmission resource used for transmitting dataincluding the status report is allocated.
 18. The apparatus of claim 15,wherein the HARQ Tx/Rx entity: receives decoding control information ofthe HARQ packet over a control channel, and checks a RetransmissionSequence Number (RSN) and a New Data Indicator (NDI) included in thedecoding control information; and determines that the HARQ packet hasbeen initially received, if the RSN is set to ‘0’ or the NDI is set to adifferent value from a previous value.